Dave Smith's Blog

After nearly one year and hundreds of flights, it’s finally time to retire the F27C Stryker R/C plane. This wasn’t necessitated by the plane or a crash, but rather my stupid attempt at modifying the airfoil to get it to roll faster. I learned the hard way that I am not an aeronautical engineer. The Stryker has been a great plane. It outlived two motors and at least 4 devastating crashes. Until I modified the wing, it flew like new. Here are some pictures to commemorate its service:

Elliot loves this plane, especially now that he can toss it around and see it flip and flop:

This is one beat-up airplane. The motor mount area of the foam got ripped out several times, and repaired very easily. The roughed up underside is due to all the concrete landings it endured behind my office building:

Here’s Elliot giving it one last throw to the ground:

I noticed that the wing tips are very rubbery and soft after all the flexing I must have put it through flying it at 70mph. What a great plane.

A moment of silence please.

That is all.

One word: crash.

I put a heavy battery in my new L-39 jet, knowing that I would eventually upgrade to a beefier motor that could make the thrust I’d need to move the heavier battery around. I was confident that it would fly stock, even with the heavier battery, because I had seen this video of it flying with my same battery on the stock motor.

I launched it three times, and the first two times it hit the deck about 20 feet out. You’d think I’d be smart enough to quit then, but I figured I just wasn’t throwing it hard enough. So I got a running start, and gave it a good solid chuck. I got my fingers to the elevator stick just in time to pull it up and out. It flew great. Did some big long circuits on low rates. Then I went for the gusto, flipped to high rates, and pumped out a wicked fast roll. This thing rolls fast! Very nice! However, coming out of the roll, a wing dipped. I think I must have been dangerously close to the stall speed. I couldn’t recover in time and it went full throttle into the ground. Elevator was ineffective, and it was all I could do to keep the wings level as it went in. Thinking back, I should have lowered the nose to gain some air speed. These jets are very different animals since there’s no prop wash over the control surfaces to help direct the plane. I mean, there really is no prop wash at all. All control authority comes from air speed.

Damage Report:

The left wing broke and fuselage broke. But never fear. I’ve already repaired it, and I have my new motor on order.

This time I’ll wait until the new motor arrives before I try any hot shot stuff.

Here’s the flight video. Please forgive all my “dang it”s after the crash. I was a little upset, needlessly so, of course. I was fine afterwards. The whole plane only cost $99 (including fan and motor), so hey, it’s easy and cheap to repair.

My good friend Cliff (a.k.a., Darth Elevator), strapped a digital video camera to his Slow Stick airplane this week and filmed me flying Randy’s Stryker around. The video captures both the Stryker take off and landing, and lots of crazy stunts. After seeing myself fly it from this angle, I’m surprised Randy lets me fly it at all. The video has been edited down to only include the shots where the Stryker is visible on camera. Here’s the video:

Spring is in the air in Salt Lake City, so it’s finally warm enough to get back into R/C flying. To that end, I ordered the new Electrifly L-39 electric ducted fan (EDF) jet. It’s getting great reviews, and I’m excited to fly it. I’ve read that the stock brushless motor is underpowered, so I’m looking into motor upgrades. I’m considering the HXT 2040 4850kv from HobbyCity.com, which ought to be a bolt-on replacement for the Ammo 3500 inrunner the plane comes with, but I’m worried it won’t give an appreciable power boost.

Stay tuned for more info, but in the mean time, check out this video of the L-39 flying with a pair of F-27 Strykers (which I have also built and flown, if you follow this blog):

And here’s the official Electrifly advertisement for the L-39:

I put together a $22 Hobby Lobby Yak 55 Profile this week, and it’s great fun. This is by far the most aerobatic plane I’ve flown. Here’s my power setup:

Here are a few videos of it in action

The takeoff

Sorry about the shaky cam at the beginning. Notice that it just jumps vertically out of my hand while rolling at about 3 rolls per second. Pretty awesome:

Some Stunts

This video shows lots of fun stuff, knife edges, loops, snap rolls, flat turns. Lots of good stuff.

Landing

This one mixes in some fun rolls and then the landing. The landing is a tad abrupt, but it works. I need to work on throttle management in my landing approaches because it just falls out of the sky if you dead stick it.

That’s all for now. Stay tuned for more photos of the plane up close so you can see how I put it together.

Here’s the video of the Easy Glider maiden flight:

Since then, I’ve had about 4 more flights, and they’ve all gone very well. The only mishap was when the canopy popped off during my last flight, and landed in the nearby river! The wind was good to me, though, and blew it over to the edge, where I was able to retrieve it. Sometimes, mother nature really is on your side in this hobby.

I finished the Easy Glider today, and took it out for its maiden flight. Here’s the setup:

• Motor: Tower Pro 2908-10 brushless
• ESC: Tower Pro 30A
• Battery: Hextronik 2200mah 20C
• Prop: 9×4.5 (will upgrade to a folding prop later)
• Servos: Hextronik 9g servos
• Radio: Spektrum DX6 with AR6000 receiver

The plane took a little longer to build than expected, mostly because I ordered the non-electric version so I had to dig out lots of foam to accommodate my battery and motor. I had a hard time fitting all the servo cables under the canopy, so I flew without it the first time. Here’s what the plane looks like:

When I launched the plain, it flew up at about 45 degrees without any sign of slowing down. I was impressed. After an altitude of about 100 feet, I killed the motor to see how it would glide. I must have pulled back too much on the elevator, because the left wing stalled and it started to roll over. Experience taught me how to handle this, so I let the nose fall down to get some airspeed, and rolled out of the stall. Then, I decided to climb a bit, and that’s when the firewall tore loose of the foam. Fortunately, I had put a layer of packing tape over it to double secure it to the fuselage, so it didn’t fall out of the sky. I was able to pilot the plane down with no problem. Any maiden flight with a good landing is a good flight, and this was no exception. I came down with spoilerons, and I’m not sure I could have come down in time without them. I would have overshot my runway by a factor of about 3.

I’ll post some video later.

With winds gusting to 15mph, I took my new R/C plane, the Stryker, out for its maiden flight. If you’ve been following the build log (part 1 and part 2), you already know that it’s outfitted with a Tower Pro 2409-12 motor, a Blue Arrow 30A ESC, an 8-cell NiMH battery (9.6V), and a 7×6 slow flyer prop. The maiden results are in:

• Flights: 3
• Aileron Rolls: 2
• Split S’s: 1 (accidental)
• Immelmans: 1
• Landings: 3
• Crashes: 0

I am very pleased with the results. The plane flies fast and responsive. Only a few clicks of right trim were needed on takeoff for level flight. The glide ratio is exactly perfect for slow, controlled, short runway landings. I am very impressed with this plane. Even with my wimpy 8-cell NiMH battery, it seems to fly around 50mph in the flats. I think when I go to LiPo, it’ll be closer to 70mph. The final speed upgrade will be a 7×7 prop, and that should put me right at 80mph. Wow.

Here’s a video of the takeoff (you can tell how windy it is by my hair blowing straight up and back):

Here’s a video of some aerobatics during the first flight. It starts with the first roll this plane has even performed, which turned into more of a Split-S since the ailerons were on low rates (50% travel):

And finally the landing. I bobbled a little on the approach, but the touchdown was nice and smooth. I love belly-scraping planes like this. They land so much better than geared planes on uneven terrain:

I was pretty nervous flying this plane for the first time, but I’m not nearly so afraid of repairing this plane as my Formosa, since it’s all one piece of foam. Hopefully I won’t have to find out how hard it is to repair.

I finished my Stryker RC plane today. The only thing I had left to do was mount the motor, which I am very pleased with. I decided to use the stock motor mount with a very small adaptation to mount the Tower Pro 2409-12 motor that I bought from unitedhobbies.com. I used a technique I read about on one of the RC forums (rcgroups, rcuniverse, wattflyer) involving the plastic lid of a soda bottle. Since the 2409-12′s mount holes are in different positions than the stock motor mount, I drilled 3 holes into the bottle cap to mount into. I used my razor blade to chop away the vertical cylinder of the lid, leaving only the flat disk, which fits perfectly inside the Stryker mount. Here’s a picture of the sode bottle lid bolted into the stock motor mount (on the other side sits the aluminum mount that came with the 2409-12 motor):

The bolts included with the motor from unitedhobbies.com were too short to fit through both the bottle lid the stock mount, so I had to buy some 2-56 metric bolts from Radio Shack for $1.99 (the motor 2409-12 mount’s holes are drilled for a 2mm bolt). From the back, you can see how the three bolts protrude with plenty of room:

The bottom bolt fits into the bottom hole of the stock mount, but the other two sit at approximately 11 o’clock and 1 o’clock. The mount is amazingly sturdy as the bottle cap and mount are squeezed in between the bolts’ washers and the aluminum mount. While working with the mount, I realized I needed to remove the bell from the motor mount to accommodate my fat fingers. After I mounted the aluminum plate, I put the motor back on using the two Allen screws. Here’s what it looks like ready to fly:

I did some glide tests and partial-power tests in my backyard today and it seems to fly level and smooth. I had to spend some quality time with my DX6 to adjust the servo travels because it seemed that when I applied full back stick, the right elevon moved farther than the left elevon. I knew that this would cause the plane to roll, so I reduced the elevator channel’s travel down to 50% in both directions. That’s what it took to make the two elevons move evenly with elevator. I setup low rates at around 70% for both elevator and aileron channels and they seem pretty good. I think I will probably fly the maiden flight with the elevator on high rates and the aileron on low rates. The maiden flight will probably happen this week some time.

For the maiden, I’ll try to borrow a friend’s Align 2200mah 3S lipo, which should provide lots of power. If it’s not available, I’ll use my 8-cell 1500mah NiMH pack. Currently the CG seems to be spot on with the 8-cell pack.

I started building a Parkzone Stryker last night. So far I’ve spent $25 on the fuselage and elevons, and this is what it looks like:

This airplane has been very easy to put together. The elevons clip on with no glue and are pre-hinged. The battery compartment is very spacious, and the servo holes are pre-cut. This took me less than an hour to do.

Here’s what I have left:

• Install the vertical fins.
• Mount a motor (considering the Tower Pro 2408-21, reverse mounted on the stock motor mount).
• Secure the battery with a velcro strap.

Here’s a shot from the back for the curious: